Producing isoprene.



UNITED STATES PATENT OFFICE.

HERMANN' A. STAUDINGER, OF KARLSRUHE, GERMANY, ASSIGN'OR TO BADISCHE ANILIN & SODA FABRIK, OF LUDWIGSHAFEN-ON-THE-RHINE, GERMANY, A COR- PORATION.

PRODUCING ISOPRENE.

1 065,182 Specification of Letters Patent.

No Drawing.

To all whom it may concern:

Be it known that I, HERMANN A. F. STAUD- INGER, subject of the Grand Duke of Baden, residing at 'Karlsruhe, Germany, have invented new and useful Improvements in Producing Isoprene, of which the following is a specification.

I have found that isoprene can be obtained in very good yield from dipentene by heating vaporized dipentene in a state of attenua-- tion, such attenuation being effected by the addition of indifferent gas, or gases, such for instance as nitrogen, or by reducing the pressure in any suitable manner. In order to obtain good yields it is desirable that the vapor be not left too long in contact With the source of heat, but that it be removed as soon as possible from the zone of high temperature. A wire heated to redness by means of an electric current is a suitable means for obtaining the necessary temperature. When the vapors are only heated to a dull red heat, less gaseous product is obtained, but the decomposition of the dipentene proceeds slowly. If the temperature,

however, be -raised considerably, a good yield of isoprene is obtained more quickly, but

the quantity of gaseous by-product is also slightly increased. The dipentene employed for the purpose of my invention can beobtained from turpentine by chemical means, or it can be produced synthetically, or the forms of dipentene which occur in nature, such for instance as limonene, can be em ployed.

Application filed August 25, 1911.

Serial No. 645,982.

Patented June 17, 1913.

The following example will serve to iJlusfrom 60 to 70 grams per hour, over a platinum wire 3 meters .in length and 0.5 millimeter in diameter, using a current of 400 volt-amperes. The temperature varies between 500 and 700 C. Pass the gases through a vessel cooled with solid carbon dioxid and isolate the isoprene by fractional distillation of the liquid obtained. The rate at which the dipentine is passed over the Wire will vary according to the conditions employed, for instance it is dependent in particular on the diameter and the length of the wire.

According to this invention yields of fifty per cent. or more of isoprene can be obtained.

Now what I claim is 1. The process of producing isoprene by heating vaporized dipentene in a state of attenuation at a temperature above 350 C.

2. The process of producing isoprene by heating vaporized dipentene under reduced pressure at a temperature above 350 C.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

HERMANN A. F. STAUDINGER.

Witnesses:

" J. Auto. LLOYD,

' JOSEPH Fnrrrnn. 

